alt.data {WeibullR.ALT}

Create a alt.data Object for Accelerated Life (Failure) Test Data

Description

This function reads life test data for a single stress level using the flexible input format also provided for "WeibullR::mleframe" to create an "alt.data" object.

Usage

alt.data(x, s=NULL, interval=NULL, stress) 

Arguments

x

Either a dataframe containing at least $time and $event columns and optionally a $qty column, or a vector of class "numeric" or "integer" with (life-)time observations.

s

An optional vector of right-censored data, or suspensions.

interval

An optional dataframe of interval data having columns specifically named "left" and "right". Left values are the last time at which no failure was evident and may be zero for discovery. Right values are the earliest time at which failure was observed.

stress

A scalar value representing the accelerating stress applied during a life test.

Details

There are several methods to passing arguments for building an alt.data object.

• If argument x is of class "data.frame", then it must contain $time and $event columns. Additional columns in the dataframe will be ignored.

• When a single unnamed vector of class "numeric" or "integer" is supplied, it is treated as a vector of (life-)time observations.

• If argument time or fail is provided, it is treated as a vector of (life-)time observations. Take care NOT to supply both time and fail in the same function call.

• If argument event is provided, it is treated as a vector of event indicators with possible values of 0 and 1. See section "Value" for more details on event vectors.

• If the x argument is not provided as a dataframe and susp is provided, it is treated as a vector of right-censored (life-)time observations (also called suspended observations or suspensions).

While "WeibullR::mleframe" is used for data sets with 3 or more failures (including intervals) alt.data will also prepare conforming dataframe for sets with less failuers or even no failures (ie. all censored items)

Value

A named list of class "alt.data". The first list item ($data) is a list with up to least three items:

$stress

A scalar value representing the accelerating stress applied during a life test.

$data

A dataframe containing the provided data formatted with "left", "right", and "qty" columns. This conforms with the output of function "WeibullR::mleframe".

References

Wayne Nelson, (1990) "Accelerated Testing", Wiley-Interscience, New York

William Q. Meeker and Luis A. Escobar, (1998) "Statistical Methods for Reliability Data", Wiley-Interscience, New York

Examples

  table2.1<-NelsonData("table2.1")
  alt_da190<-alt.data(table2.1$C190, stress=190) 
  ClassH_goal<-alt.data(20000, stress=180)